expression is provided for Gray-coded rectangular quadrature amplitude modulation (R-QAM) signals. The characteristics of Gray code mapping such as symmetries and repeated formats of the bit assignment in a symbol among bit groups are applied effectively for the simplification of the LLR expression. In order to reduce the complexity of the max-log-MAP algorithm for LLR calculation, we replace t...

AhtracrThis paper investigates encoders optimization for Hamming weight after periodic puncturing, rind discusses minimality issues that may affect the performanoe of the punctured encoders. Periodically puncturing a minimal encoder produces a higher rate encoder that may or may not be minimal. If it is not minimal, it may have a zero-output loop and it may be Catastrophic. A code search can us...

cdb is a simple, source-level debugger for ANSI/ISO C programs compiled by lcc, a retargetable C compiler. cdb is completely independent of its target architecture. This independence is achieved by embedding a small amount of itself — a ‘nub’ — in the program to be debugged and by having the compiler emit machine-independent symbol-table data and related code. This paper describes the design of...

In this paper, we investigate the performance of a downlink multiple-input multiple-output (MIMO) multi-carrier code division multiple access (MC-CDMA) system employing a receiver with iterative channel estimation (ICE). The MC-CDMA system transmits several data symbols per user and per orthogonal frequency division multiplexing (OFDM) symbol in parallel, with each data symbol being spread with...

Presented in the paper is the PLC symbol naming rules in order to simulate the virtual factory which is operated by the PLC control logic. In the PLC simulation, the corresponding model, normally called as the plant model, to the PLC receives the PLC output signal, operates virtual devices, and sends the changed PLC input signal which is updated by the virtual device movements. Therefore the pl...

In a time-varying signal-to-noise ratio (SNR) environment, symbol rate is often changed to maximize data return. However, the symbol-rate change has some undesirable effects, such as changing the transmission bandwidth and perhaps causing the receiver symbol loop to lose lock temporarily, thus losing some data. In this article, we are proposing an alternate way of varying the data rate without ...

When the Alamouti code is applied (as a space-time block code) to an OFDM system with transmit diversity, the simple Alamouti decoding requires that each subchannel is flatfading and constant over two symbol periods(Alamouti codeword period). The second requirement makes the Alamouti decoding scheme not suitable for time varying channels. In this paper, we propose a new decision directed receiv...

We propose a simple method that, given a symbol distribution, yields upper and lower bounds on the average code length of a D-ary optimal code over that distribution. Thanks to its simplicity, the method permits deriving analytical bounds for families of parametric distributions. We demonstrate this by obtaining new bounds, much better than the existing ones, for Zipf and exponential distributi...

In this paper, a novel digital modulation technique called Multi-Carrier Code Division Multiple Access (MCCDMA) is analyzed. With MC-CDMA, each data symbol is transmitted at multiple subcarriers with each subcarrier modulated by “1” or “-1” based on a spreading code. Analytical results are presented on the performance of this modulation/multiple access scheme in the downlink of an indoor wirele...

This paper discusses a code acquisition technique, for use in spread-spectrum communication system with large frequency offsets, where the frequency offset is similar to the symbol rate. This is the situation typically in satellite communications systems. The technique uses a very efficient method of performing the correlation where the frequency and time space can be searched with very little ...